Movement

• Movement

  • sensory systems provide input to the brain
  • most of the output is movements
  • we perform very complex movements
  • synchronize sensory input, lots of muscle
  • different kinds of movement
  • slow, careful, detailed, fast, automatic
• Movement pathway

  • Basics
  • primary motor cortex
  • spinal cord motor neurons
  • muscles
  • lateral and medial (anterior) corticospinal tracts:
  • lateral controls contralateral lateral muscles (arms, legs)
  • anterior controls both sides medial muscles (neck, torso)
• Cerebellum

  • also projects to the corticospinal tract
  • via the red nucleus
  • mostly inhibitory input
  • involved in;
  • fine motor control, motor patterns
  • timing of movements (through inhibition)
  • shifting attention

  
• Before moving

  • primary motor cortex executes movements
  • spinal cord and cerebellum control and coordinate movement
  • where does the planning happen?
  • inputs to the primary motor cortex
  • posterior parietal cortex
  • premotor cortex
  • supplementary motor cortex
  • basal ganglia
  • prefrontal cortex

  
• Planning motion

  • posterior parietal cortex
  • tracks the position of the body relative to objects in the world
  • related to the visual where pathway
  • involved in initial planning to move
  • activated before movement is initiated
  • damage causes apraxia: inability to perform action intentionally but can move spontaneously
  • encodes only what action is planned, the goal
  • actotopic encoding
  • independent of which parts of the body are involved
• Actotopic activation

  • the goal of the action determines the activation
• other cortical areas


  -premotor cortex

  • involved in targeting (body part to goal)
  • encodes which part of the body is involved

  -supplementary motor area

  • involved in fast sequences of action
  • also in balance, coordination of sides of body, spontaneous motion

  -prefrontal cortex

  • value of action, quality of movement, prediction
• Basal ganglia

  • part of the limbic system (not cortex)
  • involved in:
  • automation of movements, habit formation
  • controlling eye movements
  • superior colliculus (SC; in midbrain) has a retinotopic map
  • SC is inhibited by the substantial nigra
  • release of inhibition causes looking toward that point
• Disease of the basal ganglia 


  Parkinson's disease

  • caused by death of neurons in substantial nigra
  • patients have trouble initiating spontaneous movement, planning movement without external guide
  • switching between different movement patters

  Huntington's disease

  • almost entirely genetic, late onset
  • caused by massive neuronal loss, much of it in basal ganglia
  • patients have uncontrollable twitches and tremors and eventually movements and death
• Mirror neurons

  • found throughout the cortex
  • mostly in the premotor area, parietal cortex
  • respond to
  • performance of a particular movement
  • seeing the same movement performed
  • hearing the action, remembering it, reading it
  • possibly form the basis for imitation
  • controversial
  • no clear result on their function